When you change the aperture on the lens, a cam/lever at the back of the lens moves a corresponding lever in the camera, "telling" it which aperture is set.
Check that:
The cam on the lens is moving when you change aperture & isn't bent
The cam in the camera body can move freely & isn't bent.
If it looks like the two could engage when the lens is mounted.

With the lens off, try moving the camera's cam and see if the meter readings change.

Those checks *might* give you an idea of what the problem is.